fixed several PEP8 violations
removed docstring clearly inherited from contrib code
full refactor of github web hook:
  - removed unnecessary time conversions and replace it with
    dateutil.parser
  - updated dictionary keys that were hitting deprecation warnings (who
    and when for author and when_timestamp)
  - reindentation and other code sanitize
added bitbucket web status hook
Merge branch 'bitbucket' of git://github.com/DamnWidget/buildbot
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#	new file:   master/buildbot/status/web/hooks/bitbucket.py
#	modified:   master/buildbot/status/web/hooks/github.py
#	new file:   master/buildbot/test/unit/test_status_web_change_hooks_bitbucket.py
#	modified:   master/buildbot/test/unit/test_status_web_change_hooks_github.py
#	modified:   master/docs/manual/cfg-changesources.rst
#	modified:   master/docs/manual/cfg-statustargets.rst
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add relnotes for previous commit